I just upgraded a system from a 3.5 kernel to 3.12.3 and attempted to run some
new benchmarks on it. I see my test program ramps up in CPU usage for a few
seconds and then it gradually tails off. There's nothing obvious in the user
code to trigger this behavior, so I check dmesg, and see this:
[ 55.037057] JFS: nTxBlock = 8192, nTxLock = 65536
[163591.807470] perf samples too long (2758 > 2500), lowering
kernel.perf_event_max_sample_rate to 50000
[164061.362762] perf samples too long (5204 > 5000), lowering
kernel.perf_event_max_sample_rate to 25000
[167969.339513] [sched_delayed] sched: RT throttling activated
[182741.484637] perf samples too long (294588 > 10000), lowering
kernel.perf_event_max_sample_rate to 12500
[182741.484726] INFO: NMI handler (perf_event_nmi_handler) took too long to
run: 36.665 msecs
[182822.633084] perf samples too long (292359 > 20000), lowering
kernel.perf_event_max_sample_rate to 6250
[182905.606119] perf samples too long (290291 > 40000), lowering
kernel.perf_event_max_sample_rate to 3250
[199384.293514] perf samples too long (288142 > 76923), lowering
kernel.perf_event_max_sample_rate to 1750
[208507.301027] perf samples too long (285964 > 142857), lowering
kernel.perf_event_max_sample_rate to 1000
[208528.976208] perf samples too long (283799 > 250000), lowering
kernel.perf_event_max_sample_rate to 500
Why is the kernel throttling my server?
--
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/
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